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The Global Carbon Cycle




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The Global Carbon Cycle Tom Bibby September 2003 [email protected] [email protected] The Carbon Cycle - Look at past climatic change; as controlled by the carbon cycle. - Interpret the influence of human changes (Anthropogenic Perturbations) - Economic and Trade Policies Earth Venus States of water in the solar-system The Faint Young Sun Paradox The greenhouse effect This false-color Terra satellite image of Earth shows infrared heat escaping to space. Greenhouse gases trap such heat and warm our planet. Relative percentage composition of greenhouse gases in the Earth’s atmosphere Distribution of carbon reservoirs on Earth Pools Quantity (gt) Atmosphere 720 Oceans 38,400 Total inorganic 37,400 Surface Layer 670 Deep layer 36,730 Total Organic 1,000 Lithosphere Sedimentary carbonates >60,000,000 Kerogens 15,000,000 Terrestrial biosphere (total) 2,000 Living Biomass 600-1,000 Dead Biomass 1,200 Aquatic biosphere 1-2 Fossil fuels 4,130 Coal 3,510 Oil 230 Gas 140 Other (peat) 250 Falkowski et al, 2002 Science, Vol 290, 291-296 Values of carbon exchange between reservoirs Carbon Degassing MÖrner and Etiope, Global and Planetary Change 33 (2002) 185-203 Methane Hydrates Cross-section through the Earth The Ring of Fire Chemical weathering – Export of CO2 From the atmosphere The hydrological cycle Chemical Weathering Calcite (Carbonate) compensation depth (CCD) -- The depth in the ocean below which material composed of calcium carbonate is dissolved and does not accumulate on the sea floor Factors effecting the rate of chemical weathering Temperature : Rate of chemical reactions Precipitation: Amount of H2O Vegetation: Efficiency of delivery of CO2 to the soil Atmospheric CO2 Levels Myrs ago Falkowski and Raven 1997 Faint Young Sun Paradox: Negative feedback controls. Faint Young Sun paradox: Controlled by the Carbon cycle Rate of Tectonic Movement The Earth’s Orbit Long-term changes in tilt: Changes in the tilt of the Earth’s axis have occurred on a regular 41,000-year-cycle Long-term changes in eccentricity: The eccentricity of the Earth’s orbit varies at periods of 100,000 and 413,000 years. Long-term changes in precession: The precessional index changes mainly at a cycle of 23,000 years Review of Lecture 1 Aim:Cover the long-term processes of the carbon cycle. - CO2 release into the atmosphere. - Removal of CO2 from the atmosphere via chemical weathering. These processes have existed in a dynamic equilibrium that has kept the Earth’s climate relatively constant. The Faint Young Sun Paradox Atmospheric CO2 Levels Myrs ago Falkowski and Raven 1997 The Carbon Balance each year... • 6.3 Gt from fossil emissions • 1.6 Gt emitted from land-clearing • Leaving a net 7.9 Gt in the atmosphere (estimated) The Balance each year... • 6.3 Gt from fossil emissions • ca. 1.6 Gt emitted from land-clearing • 1.7 Gt net uptake into ocean systems • 3.0 Gt into terrestrial systems • Leaving a net 3.2 Gt in the atmosphere The evolution and global effect of photosynthetic organisms Myrs ago






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